Water-permeable materials are recently more and more widely used for forming footpaths, roadways, plazas, dry riverbeds, banks, roofs of buildings, parking spaces, swimming pool sides and the like in order to promote the drainage. Water-permeable materials not only improve environment by virtue of their good drainage, but also have good outer appearances.
These water-permeable materials are in the form of plates and blocks and are produced by molding a composition for forming the water-permeable material, which composition generally comprises aggregate grains, a synthetic resin binder and a curing agent of the synthetic resin binder. The aggregate grains contained in the compositions for forming the water-permeable materials are naturally occurring stones, grains obtained by processing naturally occurring stones, balls made of ceramics such as pottery, spherical sintered grains made of a mixture of wood-containing clay and clay feldspar. As the synthetic resin binder, epoxy resins are generally employed. The epoxy resins employed are those which have glycidyl groups at the end, such as bisphenol A type and bisphenol F type epoxy resins which are copolymers of bisphenol A or bisphenol F and epichlorohydrin. Such a synthetic resin binder is added to the aggregate in an amount that it can just bind the aggregate grains so that the obtained material exhibits water permeability (see, for example, Japanese Laid-open Patent Application (Kokai) Nos. 51-133350, 1-51349 and 2-148003.
The water-permeable materials are generally molded as follows:
(1) Aggregate grains and a curable resin liquid in an amount necessary for binding the aggregate grains are sufficiently mixed; PA1 (2) The obtained composition is spread on a conditioned floor to a uniform thickness using a rake or the like; and PA1 (3) A flat surface is given to the composition using a trowel or the like. PA1 (i) The weatherability is insufficient and the material is deteriorated to become brittle or colored with time. Such deterioration mainly occurs in the regions of epoxy resin used as a binder. PA1 (ii) The material is elongated or shrunk due to the stress given by the repetition of heating and cooling, or to the external load, so that cracks tend to be formed. Although formation of the cracks due to the elongation and shrinkage can be prevented by providing joints, providing joints is troublesome and appearance of the material is also deteriorated. PA1 (iii) The conditions for application of the composition are influenced by the weather, that is, by rain, dew, snow, freezing or the like. As a result, curing may be insufficient or the material may be whitened. In order to avoid such undesired consequences, it is necessary to apply the composition only in good weather. Therefore, the time period necessary for the construction may be prolonged. PA1 (iv) The chemical resistance of the materials is insufficient. Therefore, if an acid, alkali, soft drink such as juice, organic solvent or the like is attached to the material, the material is easily colored or deteriorated. PA1 (1) When the water-permeable material is applied with a trowel, the resin and the aggregate adhere to the trowel surface. As a result, the slipperiness of the trowel is deteriorated, so that the efficiency of the operation is decreased and the quality of the finishing is poor. PA1 (2) In order to remove the material attached to the trowel surface so as to improve the slipperiness, a thinner (organic solvent) is used. However, use of a thinner presents the following problems: PA1 (3) Because of the above-mentioned (1) and (2), a machine cannot be well used. PA1 providing a composition comprising aggregate grains, a sulfur-modified epoxy resin and a curing agent for the sulfur-modified epoxy resin; and PA1 molding the above-mentioned composition into a desired shape and curing the composition. PA1 (i) Since the sulfur-modified epoxy resin is used as the resin component, the flexibility and elongation of the resin are large, so that the material well follows deformation. Therefore, cracks are hardly formed, so that it is not necessary to frequently cut joints during the application operation. PA1 (ii) Ease of application is excellent. For example, the composition can be applied even if it rains. This is because that the polysulfide-modified epoxy resin is contained as the resin component, so that the curing rate is hardly decreased by water and deterioration of performance after curing hardly occurs. However, care should be taken that large external force or sustaining external force by water is not exerted during the resin is not cured. PA1 (iii) Even if the material contacts water, the adhesiveness is hardly reduced. The resin regions are hardly whitened and the material is not whitened by dew. PA1 (iv) The material has a good weatherability. Therefore, the material is hardly deteriorated (cracked or colored) with time by various conditions such as weather. PA1 (v) The material has a good chemical resistance. Therefore, the material exhibits excellent resistance to various food solutions, acidic rain, sewage and the like. PA1 (vi) By making water to exist on the surface of the trowel, finishing surface of the finisher and/or on the water-permeable material during the application operation, the operation efficiency is largely promoted and a material with high performance is obtained.
Although the operation using the trowel is similar to that for applying a cement mortar, application of the water-permeable material is different from the application of the cement mortar in that aggregate grains covered with the resin liquid are applied. Since the viscosity of the resin liquid increases with time because of the proceeding of the reaction, the composition adheres to the trowel, so that it is necessary to frequently wipe off the composition using an organic solvent such as a thinner. Thus, it is not practical to carry out the application by a machine.
The water-permeable materials made from the conventional compositions described above have the following drawbacks:
It is thought that these problems with the water-permeable materials are mainly caused by the synthetic resin binder components.
The conventional method for applying the water-permeable material has the following problems:
(i) Odor and safety. PA2 (ii) The solvent attached to the surface of the trowel dissolves and flow out the resin on the surfaces of the aggregate grains in the finishing step, so that the binding force of the aggregate grains in the vicinity of the surface is decreased. PA2 (iii) Spilt organic solvent dissolves the resin on the aggregate grains inside the material, so that the strength of the portion of the layer is decreased and the strength of the material is thus made non-uniform. PA2 (iv) The solvent from the surface of the trowel dissolves the resin layer in the surface of the material, so that the curing of the resin is delayed. As a result, the viscousness of the surface is retained, so that dusts tend to be attached. PA2 (v) The solvent is evaporated during operation and the trowel tends to become heavy. Therefore, it is difficult to uniformly slip and press the trowel. As a result, the flatness of the material is not good and the surface of the material is irregular. Thus, the quality of the finishing is poor and the outer appearance is not good.
The object of the present invention is to make an improvement such that a water-permeable material which has good weatherability and chemical resistance, in which cracks are hardly formed, can be easily produced. Another object is to overcome the above-mentioned problems on the application of the water-permeable material, thereby improving the efficiency of the application and performance of the finished product.